350 APPENDAGES OP THE EYE. 



Function. To raise the eye. It covers the third, nasal, 

 and optic nerves, with the ophthalmic artery. 



Eectus inferior (or depressor oculi,) situated on the infe- 

 rior margin of the optic foramen by a ligament common to 

 this muscle, and the external and internal rectus, called 

 the ligament of Zinn, and from the fibrous sheath of the 

 optic nerve, passes forward beneath the optic nerve, and 

 upon the floor of the orbit, separated from it by the in- 

 ferior oblique muscle and some adipose matter, and ter- 

 minates in a tendon which is inserted into the under sur- 

 face of the sclerotica, near the cornea. 



Function. To depress the eye. 



The Eectus externus, (or abductor oculi^) situated on the 

 outer portion of the orbit, is the longest of the recti mus- 

 cles. It arises by two heads, one from the external margin 

 of the optic foramen and optic sheath, the other from the 

 ligament of Zinn. The muscle passes forward, ends in a 

 tendon which is inserted into the outer surface of the scle- 

 rotica near the cornea; between the two heads of this mus- 

 cle, the third, nasal, and sixth nerves pass, the latter nerve 

 being wholly spent upon this muscle. It is separated from 

 the optic nerve and the ball of the eye, by the lenticular 

 ganglion, ciliary vessels, nerves, and fascia. 



Function. To abduct or roll the eye outward. 



The Eectus internus, (or adductor ocutt,) situated upon the 

 inner portion of the orbit, arises from the inner margin of 

 the optic foramen by the ligament of Zinn, and from the 

 optic sheath it passes forward, becomes tendinous, and is 

 inserted into the inner surface of the sclerotica near the 

 cornea. 



Function. To roll the eye inward. 



The dbliquus superior, (or troclileator^) situated at the 

 upper and inner part of - the orbit, is a long and slender 

 muscle, arising by a small tendon from the inner margin of 

 the optic foramen, and from the sheath of the optic nerve; 

 it proceeds forward and upward, along the os-planum to the 

 internal angular process of the frontal bone, beneath and 

 rather behind* which, this muscle forms a round tendon 



